The idea of synchronizing two devices using a combination of location and motion was originally presented by Holmquist et al. (see Holmquist, Lars Erik and Mattern, Friedemann and Schiele, Bernt and Alahuhta, Petteri and Beigl, Michael and Gellersen, Hans (2001) Smart-Its Friends: A Technique for Users to Easily Establish Connections between Smart Artefacts. In: UbiComp '01: Proceedings of the 3rd international conference on Ubiquitous Computing, 1900-01-01, Atlanta, Ga., USA). This system was built using specialized hardware based on the Smart-Its sensor nodes. Each device had an accelerometer (sensor) and a radio transceiver. By monitoring the motion signature of all devices in range, the system could determine if two or more devices were being shaken together at the same time. It could then open up a dedicated wireless connection between them.
An alternative version of the same mechanism was presented as “bumping” (see Hinckley, K., Ramos, G., Guimbretiere, F., Baudisch, P., and Smith, M. (2003) Synchronous Gestures for Multiple Persons and Computers. In Proc. UIST 2003 Symp. on User interface Software and Technology, Vancouver, Canada, pp. 149-158). This was implemented by attaching the accelerometer (sensor) to mobile computers connected to the same wireless network. Today the necessary hardware is available in standard smartphones and tablets. A variant method was introduced around the same time, Synctap, which instead uses the standard buttons on two devices on the same network (see Jun Rekimoto, Yuji Ayatsuka, Michimune Kohno. SyncTap: An Interaction Technique for Mobile Networking. Human-Computer Interaction with Mobile Devices and Services Lecture Notes in Computer Science Volume 2795, 2003, pp 104-115).
A commercial version of this interaction technique was released in 2009 as Bump for iPhone and Android (see www.bu.mp, and US Patent Application Publications 2011/0191823, US 2011/0191438 and US 2011/0187652, all published on Aug. 4, 2011). It uses the same principle of co-located motion. It then compares synchronous motion signatures of devices with the approximate same physical location. When two phones are synchronously “bumped”, they can establish a connection over a standard internet protocol, in order, for instance, to exchange photos or business cards.